prj2.c

/********************************************************************************
 * Name				:infix postfix
 * Author			:Prapanch J
 * Description		        :c- Program 
 * Version			:1.0
* Date				:/10/23
 * ******************************************************************************/
#include <stdio.h>
#include <ctype.h>
#include <string.h> 

int top = -1;
char stack[20];

void push(char);
int pop();
int priority(char);

int main() {
    push('(');
    char infix[20], *p;
    printf("Enter the infix expression :\n");
    scanf("%s", infix);
    p = infix;
    printf("\nIt's postfix expression is :\n");
    while(*p != '\0') {
        if(isalnum(*p))
            printf("%c ", *p);
        else if(*p == '(')
            push(*p);
        else if(*p == ')')
            while(pop() != '(');
        else {
            while(priority(stack[top]) >= priority(*p)) { 
                pop();
            }
            push(*p);
        }
    p++;
    }
    while(top >= 0){
        pop();
    }
}

void push(char pushElement) {
    top++;
    stack[top] = pushElement;
}

int pop() {
    char x;
    x = stack[top];
    if(x != '(')
        printf("%c ",x);
    top--;
    return x;
}